Importance: Neurochemical studies in human aggression point to a modulatory role for a variety of central neurotransmitters. Some of these neurotransmitters play an inhibitory role, while others play a facilitatory role modulating aggression. Preclinical studies suggest a facilitatory role for inflammatory markers in aggression. Despite this, to our knowledge, no studies of aggression and inflammatory markers have been reported in psychiatric patients or in individuals with recurrent, problematic, impulsive aggressive behavior.
Objective: To test the hypothesis that plasma inflammatory markers will correlate directly with aggression and will be elevated in individuals with recurrent, problematic, impulsive aggressive behavior. DESIGN, SETTING, AND PARTICIPANTS Case-control study in a clinical research program in impulsive aggressive behavior at an academic medical center. Participants were physically healthy individuals with intermittent explosive disorder (n = 69), nonaggressive individuals with Axis I and/or II disorders (n = 61), and nonaggressive individuals without history of an Axis I or II disorder (n = 67).
Main outcomes and measures: Plasma levels of C-reactive protein and interleukin 6 were examined in the context of measures of aggression and impulsivity and as a function of intermittent explosive disorder.
Results: Both plasma C-reactive protein and interleukin 6 levels were significantly higher in participants with intermittent explosive disorder compared with psychiatric or normal controls. In addition, both inflammatory markers were directly correlated with a composite measure of aggression and, more specifically, with measures reflecting history of actual aggressive behavior in all participants.
Conclusions and relevance: These data suggest a direct relationship between plasma inflammatory processes and aggression in humans. This finding adds to the complex picture of the central neuromodulatory role of aggression in humans.